I have different nail paint colors, but I don't have skin or golden. Is it possible to make these colors by using two or more different nail paints?
Skin color can be mixed if you have white, red, and yellow nail polish. Provided these colours have equal opacity and color strength, you can get a good idea of what the proportions should be here.
For a gold coloured mixture the process is the same, unless you need it to have the luster that is characteristic of gold. If you have silver or another metallic nail polish with such a specular effect, you could try adding yellow to it.
Another option is to combine several yellow hues. Looking at this picture:
you can easily distinct three different hues (by eye, or using photoshop or a similar image editing tool), that can be mixed with the same three colours you would use to create the skin colour.
Uploading the image to an online colour palette creation tool, like coolors.co, you can extract the colors quicker and easier.
The phrase "skin colour" is a bit ambiguous, but mixing all three primary colours or any two complimentary (particularly orange & blue) gives you a great brown that can be lightened with white if necessary. Here's a WikiHow about it.
Gold would be really hard, because you want it to reflect light. If your starting colours aren't reflective, it'll never look how you want. If you want to invest in one gold polish, my favourite is Essie's Good As Gold. It's super shiny, not too streaky and catches the light realistically.
I'd be cautious mixing two types of nail polish at all though! I've tried it before and ended up with a goopy mess that never really dried.